1. Field of the Invention
The present invention concerns safety hooks with an open body and a pivoting closure finger, in which locking is assured by a transverse locking lever engaging between the pivoting closure finger and an opposite portion of the safety hook body to selectively prevent pivoting of the locking finger in the opening direction.
2. Description of the Prior Art
Safety hooks of the above kind that are locked automatically by a transverse lever are described amongst others in documents FR 2 439 330 A, FR 2 485 658 A and U.S. Pat. No. 4,621,851 A.
In the above documents, the safety hook comprises a safety hook body having an opening selectively closed by a pivoting finger articulated at its first end about a transverse rotation pivot, with a transverse locking lever mounted to be able to pivot about a lever pivot between a locking position, in which it is engaged between the pivoting finger and an opposite portion of the body to prevent rotation of the pivoting finger and toward which it is biased by spring means, and an unlocked position, in which it releases the pivoting finger so that it can rotate in the opening direction. In documents FR 2 439 330 A and FR 2 485 658 A the pivot of the locking lever is in said opposite portion of the body, and the free end of the locking lever engages over the pivoting finger. In document U.S. Pat. No. 4,621,851 A, the pivot of the locking lever is at the free end of the pivoting finger, and the free end of the locking lever engages against the opposite portion of the body.
In documents FR 2 485 658 A and U.S. Pat. No. 4,621,851 A, the locking lever is generally rectilinear, entirely engaged between the pivoting finger and the opposite portion of the body, near the free end of the pivoting finger. As a result, the locking lever reduces the opening capacity of the safety hook, and constitutes a component that is relatively inconvenient to operate, necessitating the use of the thumb to press it perpendicularly to the movement of the pivoting finger in the opening direction. This device is therefore not suitable for mountaineering use or for working in high places, where safety conditions must be complied with without necessitating difficult and irksome intervention by the user. What is more, there is nothing to prevent pivoting of the locking lever, which can therefore be unlocked unintentionally.
In document FR 2 439 330 A, the transverse locking lever is at a greater distance from the free end of the pivoting finger, which improves the opening capacities. Also, the locking lever is L-shaped with a longitudinal branch that projects radially beyond the opposite portion of the body, which makes the locking lever more accessible for manipulation. However, locking is not sufficiently reliable because it is assured by two parallel branches at the end of the locking lever which constitute relatively weak components that may be deformed and spread apart in use. Also, the operator must be sure to press on the locking lever before pressing on the locking finger to open it, failing which it is impossible to pivot the locking lever. What is more, the locking lever projects away from the body in an exaggerated manner, and constitutes a protruding component that can interfere with use and to which force can be applied unintentionally.
In the above document, a sliding ring, mounted on the opposite portion of the body, can immobilize the locking lever to prevent it from pivoting toward the unlocked position. The drawback of this is that it is therefore necessary to manipulate the locking ring each time so that the locking lever can then be manipulated to unlock the safety hook.
Document JP 07 031 687 A describes a safety hook in which a generally rectilinear transverse locking lever is articulated at a first end on a lever pivot at an intermediate position on the pivoting finger, and cooperates via lateral L-shaped slots in its second end with opposite lateral bearing lugs of the body of the safety hook. A manipulator lever, separate from the locking lever, is articulated on the opposite part of the body and pushes the free end of the locking lever laterally to unlock the safety hook by rotating the locking lever. The structure is more complex and costly, and has an increased risk of jamming in the event of accidental ingress of sand or mud between the many moving parts or into the L-shaped slots. With this safety hook the operator must also be sure to press the manipulator lever before pressing the pivoting locking finger to open it, failing which it is impossible or very difficult to pivot the locking lever. This complicates operation. Furthermore, there is nothing to prevent pivoting of the locking lever, which may become unlocked unintentionally.
The problem addressed by the present invention is that of designing a new hook structure which is locked automatically by a transverse locking lever, which assures both reliable and effective locking, a maximum opening capacity of the safety hook, and great ease of use to change from the closed and locked position to the open and unlocked position.
The invention equally aims to design a safety hook structure of the above kind that is particularly simple and inexpensive to manufacture.
Optionally, the structure of the safety hook in accordance with the invention must assure selective immobilization or permanent releasing of the locking lever, enabling the user to choose between single locking or double locking.